Also update it to more closely match the persisted version which has the
v1 and v2 only fields as optional.
Refactor ChannelAuthProof to support both v1 and v2 channel
announcements:
- Add Version field to distinguish v1 from v2 proofs
- Wrap v1-specific fields (NodeSig1/2, BitcoinSig1/2) in fn.Option
since v2 doesn't use them
- Add optional Signature field for v2's single schnorr signature
- Add constructor functions NewV1ChannelAuthProof and
NewV2ChannelAuthProof to enforce correct initialization
- Add getter methods (NodeSig1(), BitcoinSig1(), etc.) that safely
unwrap options, returning empty slices when not present
The IsEmpty() check is updated to handle both versions correctly.
Both stores validate v1-only for now.
Elle Mouton
7a260ee103